Die for producing self-locking threaded fastener



March M, 1967 L. F. HAMPTON DIE FOR PRODUCING SELF-LOCKING THREADEDFASTENER 3 Sheets-Sheet l Original Filed Aug. 12, 1960 HGZA I MINOR DIA.STOCK DIA.

INVENTOR LYNN F HAMPTON MAJOR DIA.

ATTORNEYS March 14, 1967 L. F. HAMPTON 3,398,645

DIE FOR PRODUCING SELF-LOCKING THREADED FASTENER Original Filed Aug. 12,1960 3 Sheets-Sheet 2 STOCK DIA.

INVENTOR.

LYNN F. HAMPTON ATTORNEYS March 14, 1967 1... F. HAMPTON DIE FORPRODUCING SELF-LOCKING THREADED FASTENER 5 Sheets-Sheet 3 Original FiledAug. 12, 1960 ATTORNEYS United States Patent Office 3,388,645 PatentedMar. 14, 1967 4 Claims. c1. 72-469) This invention relates toself-locking threaded fasteners and die app-artus for producing same.

This application is a division of my prior application Ser. No. 49,267filed Aug. 12, 1960, now abandoned.

In general the threaded fastener of the present invention includes anelongated shank portion provided With a plurality of thread convolutionsforming spaced root portions and crest portions. A protruding portionfor engagement with the crests on the threads of a coacting threadedelement is formed between two adjacent convolutions with said protrusionhaving a configuration such that its radially outward extensionprogressively increases along a root portion and then progressivelydecreases along said root portion.

In accordance with the present invention it has been found that a threadinterference protrusion of this configuration progressively engages andsmoothly deforms the crests on the thread convolutions of a coactingthreaded element such that the convolutions are effectively de formedinto resilient locking engagement with the thread ed element of thepresent invention.

As another aspect of the present invention a novel thread rolling diemeans is provided that serves to form the above described threadinterference protrusion on self-locking fastener constructed inaccordance with the present invention.

It is therefore an object of the present invention to provide animproved self-locking threaded fastener that includes a threadinterference protrusion of novel configuration and gradually andsmoothly deforms and resiliently engages convolutions on a coactingthreaded element.

It is another object of the present invention to provide a threadrolling die of novel construction for forming self-locking threadedfasteners in accordance with the present invention.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings wherein a preferred form of embodiment of the invention isclearly shown.

In the drawings:

FIG. 1 is a side elevational view of a self-locking threaded fastenerconstructed in accordance with the present invention;

FIG. 2 is a sectional view of the shank of the fastener of FIG. 1, thesection being taken along the line 22 of FIG. 1;

FIG. 2A is a cross-sectional view looking along line 2A2A in FIG. 1;

FIG. 3 is a partial perspective View of a thread rolling die constructedin accordance with the present invention;

FIG. 4 is a partial plan view of a pressure applying surface of the diemeans of FIG. 3; and

FIG. 5 is an end elevational View, partially in section of the die meansof FIGS. 3 and 4, the section being taken along the line 55 of FIG. 3.

Referring in detail to the drawings, a self-locking threaded fastenerconstructed in accordance with the present invention is indicatedgenerally at in FIGS. 1 and 2 and includes a shank portion 22 and a headportion 24.

Shank portion 22 includes a plurality of thread convolutions that formspaced crest portions, two of which are indicated at 26 and 27, locatedbetween spaced root portions 28. The root and crest portions areconnected by flank portions, two of which are illustrated at 30 and 32.

With continued reference to FIGS. 1 and 2 a thread interference portionindicated generally at 34 is integrally formed between the two adjacentcrest portions 26 and 27 and includes a leading end 36 and a trailingend 38.

As best seen in FIG. 2, the radial outward extension of protrusion 34progressively increases as it extends circumferentially around the shankof the screw from leading end 36 to a location 40 at which the radiallyoutward extension of protrusion 24 begins to decrease at a locationindicated at 43 in FIG. 2 and continues to progressively decrease to thetrailing end 38.

Fastener 20 can, if desired, be provided with additional threadinterference protrusions of the configuration just described, one ofsaid additional protrusions being indicated at 34-A.

Reference is next made to FIGS. 35 which illustrate a novel threadrolling die construction for forming threaded fasteners of the typeillustrated in FIGS. 1 and 2. The die includes relatively shiftable diemembers indicated generally at 44 and 46. Both of the die membersinclude a face 48 provided with a plurality of crest portions 50 androot portions 52.

Longitudinally extending slots 54 and 56 are machined into the faces 48of die members. The distance D between datum plane 58 and 60- lyingalong the bottom of the slots 54 and 56 is preferably established suchthat it is equal to the diameter of the bar stock from which thefasteners are formed. With this arrangement the slots 54 and 56constitute longitudinally extending paths that extend across the dieface 48 along which paths there is no rolling or deformation of the barstock.

With reference to FIG. 5, longitudinally extending slots 54 and 56actually appear as diamond shaped segments 80, 82, 86, and 88 since whena grinder is passed longitudinally along die face 48, in a directionparallel with upper edge 62, the path 64 of the grinding Wheel willintersect, so far as the illustrated portion of the die face isconcerned, only the crests 66 and 88 and the path 84 of the grindingwheel will intersect only the crests 90 and 92.

When the grinding wheel is moved along path 64 to form the depression 56it will not engage the root portions 70, 72, and 74. Similarly, when thegrinding wheel is moved along the path 84 to form the groove 54 it willnot engage the root portions 71, 73, and 75. It will be understood thatthe maximum depth of grind will occur where the grinding wheel passesthrough the crests 66 and 68 and the crests 90 and 92. Where thegrinding wheel passes through these crests the maximum depth of grindwill occur at the central portions 76 and 78 of the diamond shapedsegments 80 and 82.

In operation the bar stock is fed betweenthe relatively shiftable threadrolling die members 44 and 46 whereby the bar stock is caused to rollalong faces 48 of the die members. The crests on the die members, suchas crests 66 and 88, which are intersected by the ground groove 56 forma root section 28 provided with a protrusion such as is seen at 34 inFIGS. 1 and 3. The crests that are intersected by the groove 54, whichis intersected by the diamond shaped segments 86 and 88, form a rootsection and a corresponding protrusion such as is seen at 34-A in FIGS.1 and 3. As the bar stock progresses along the die faces 48 of diesections 44 and 46 the protrusions 34 and 34-A will roll into thesuccessive ground diamond shaped sections lying along the paths 64 and84 of the grinding wheel.

In fabricating bolts in accordance with the present invention it hasbeen found that eflicient thread interference is obtained when the stockdiameter is equal to the pitch diameter of the thread such that theunrolled portions forming the thread interference protrusions 34 and34-A protrude outwardly from the minor or root diameter for a distanceequal to approximately one-half of the distance between the rootportions and the crest portions of the thread. This is achieved byestablishing the depth of grooves 54 and 56, FIG. 5, so as to equalone-half the depth of the root portion 52 relative to the die face 48,seen in FIG. 5, and by establishing the distance between the confrontingdie faces 48 so that the distance between the datum planes 58 and 60lying along the bottoms of the groove 54 and 56 is equal to the diameterof the bar stock. This is best illustrated in FIG. 5.

While the form of embodiment of the present invention as hereindisclosed constitutes a preferred form, it is to be understood thatother forms might be adopted, all coming Within the scope of the claimswhich follows.

I claim:

1. An improved thread rolling die means comprising, in combination,first and second relatively movable die portions; a plurality oflongitudinally extending crests on the face of one of said die portions,the longitudinal axes of said crests being inclined relative to thelongitudinal axis of one of said die portions, said face of said dieportion including a groove intersecting said crests, the horizontalsides of said groove being substantially parallel with the longitudinalaxis of said die portion.

2. An improved thread rolling die means comprising, in combination,first and second relatively movable die portions; a plurality oflongitudinally extending crests and root sections on the face of one ofsaid die portions, the longitudinal axes of said crests being inclinedrelative to the longitudinal axis of one of said die portions, said faceof said die portion including a groove intersecting said crests, thedepth of said groove being substantially equal to one-half the distancebetween said crests and root sections.

3. An improved thread rolling die means comprising, in combination,first and second relatively movable die portions; a plurality oflongitudinally extending crests and root sections on the face of one ofsaid die portions, the longitudinal axes of said crests being inclinedrelative to the longitudinal axis of one of said die portions, said faceof said die portion including a groove intersecting said crests, thelongitudinal axis of said groove being substantially parallel with thelongitudinal axis of said die portion, the depth of said groove beingsubstantially equal to one-half the distance between said crests androot sections.

4. An improved thread rolling die as defined in claim 1, the depth ofsaid grooving intersecting said crests being substantially equal toone-half the distance between said crests and root sections.

References Cited by the Examiner UNITED STATES PATENTS 1,973,201Fassinger 7288

1. AN IMPROVED THREAD ROLLING DIE MEANS COMPRISING, IN COMBINATION,FIRST AND SECOND RELATIVELY MOVABLE DIE PORTIONS; A PLURALITY OFLONGITUDINALLY EXTENDING CRESTS ON THE FACE OF ONE OF SAID DIE PORTIONS,THE LONGITUDINAL AXES OF SAID CREST BEING INCLINED RELATIVE TO THELONGITUDINAL AXIS OF ONE OF SAID DIE PORTIONS, SAID FACE OF SAID DIEPOR-